Electrostatic chucks of sintered ceramic, which are made by interposing an electrode between ceramic substrates of alumina or the like and sintering the arrangement, apply an electrostatic adsorption-use power to the internal electrode and thereby adsorb a substrate such as a silicon wafer or the like by an electrostatic force. To supply the electrostatic adsorption-use power to the internal electrode, electrostatic chucks of this type include an implemented arrangement in which a portion of a conductor in continuity with the electrode is exposed at a face on a side opposite the electrostatic adsorption face of the ceramic substrate, and a power supply-use connector is joined to the electrode, and the like.
In Patent Document 1, for a portion to connect an electrode built into a ceramic substrate with external wiring for supplying the electrostatic adsorption-use power, a hole having a bottom face at the same face as a formed face of the electrode is formed in the substrate, and a bottom face portion joining material is joined from the bottom face of the hole to the exposed electrode.
In Patent Document 1, a technique is disclosed for an electrostatic chuck made of sintered ceramics using a sintering process in which the electrode is interposed between ceramic substrates. In the technique, an opening is provided in the substrate after the ceramic sintering process, which includes Hot Isostatic Press (HIP) processing, and, at the opening, the electrode is joined to bottom face portion joining material. As methods to provide the opening in the substrate, processes such as cutting and grinding using diamond tools, laser machining, ultrasonic machining, and sandblasting are used.
Further, Patent Document 2 discloses a technique whereby a fixed hole, piercing the internal electrode, is provided in the sintered ceramic substrate, and a metalized layer is formed on the internal walls of the fixed hole.
Here, a thickness of the built-in electrode should generally be not more than 20 micrometers (μm). However, an accuracy of a machining position of the cutting process using the diamond tool is not less than 10 μm. Hence, there are cases in which a bottom of the hole opened in the cutting process does not reach the internal electrode, and cases in which an opening is formed to a greater extent than necessary by piercing through the internal electrode. In the case in which a hole piercing through the internal electrode is formed, an insulating layer between a bottom face of the hole piercing through the internal electrode and a material to be adsorbed gets thinner, resulting in the risk of a drop in reliability with regard to mechanical strength and/or electrical insulation.